For the testing of the behaviour of missiles provided with a seeker the so-called HWIL-simulation method is common (HWIL=Hardware-in-the-loop). Therein the seeker of a real missile is subjected to radiation, as it would receive it in real action. Then the reaction of the missile or of the seeker on this radiation is picked-off and, for example, applied to a computer, which simulates the aerodynamic behaviour of the missile. With this method the problem arises, to simulate the radiation, for example radar radiation, from the target received by the seeker in real action. In free space the radiation from the target impinges only in direct line upon the detector of the seeker. There are no walls or the like present, at which the radiation is reflected. These conditions have to be simulated in laboratory.
For this purpose, radar anechoic chambers are known. That are big halls, in which the total missile or seeker to be tested is arranged. The walls of these halls are provided with a plurality of tips arranged closely side-by-side. This shape of the walls prevents the radar rays emanating from a transmitter from being reflected at the walls into the direction to the seeker. This structure ensures, that radar rays are absorbed vere quickly by these walls. In this way the characteristic of free space not to provide radar echo is simulated.
Different methods are used in these radar anechoic chambers for the simulation of moving targets transmitting radar rays:
It is known to transform the movement of seekers and targets from the inertial reference system into the line-of-sight reference system and to electrically correct the signals in the seeker. With this method the target, that is the transmitter of the radar signals, is stationary. The movement of the target is simulated and thus is not represented physically. However, this solution does not take into account some problems of real seekers. It is not equivalent to an arrangement having a target actually moved in space relative to the seeker.
Furthermore it is known to physically move a radar transmitter relative to the seeker within a radar anechoic chamber by means of mechanical transport devices. The angular ranges of the line-of-sight possible to simulate in this way are rather limited. Large angular ranges, in which the line-of-sight is variable, require large dimensions of the anechoic chamber and expensive transport devices for the radar transmitter.
Furthermore a device is known, in which the movement of the target is simulated by phase controlled antennas in the anechoic chamber. Thus, an antenna serving as radar transmitter is not moved therein, but a row of stationary antennas is provided, which are controlled with regard to amplitude and/or phase, such that a moving apparent radiation center is obtained. Depending on the required line-of-sight angular range and on the required angular accuracy, this type of simulation of moved targets requires a very large number of expensive antennas (see U.S. Pat. Nos. 4,660,041 and 4,621,265).
Common to all of the known solutions is that they are very expensive.
It is the object of the invention to simulate, at a seeker responding to radar, the conditions of free space with a moving target emitting radar radiation, with an expenditure as low as possible.
It is a further object of the invention to simulate large azimuth and elevation angles of the line-of-sight with a device of the type defined in the beginning.
According to the invention this object is achieved with a device of the type defined in the beginning in that
Thus, there is not need for an expensive hall-like anechoic chamber, in which the seeker head is arranged, but a hollow body serves as anechoic chamber, which is movable around the seeker head. The shape of this hollow body is such that it acts as ray trap, that means that the radar radiation impinging upon the walls of the hollow body cannot be reflected in the direction towards the seeker head even if it is reflected by this walls. Thus "indirect" radar radiation or radar echo is safely prevented from reaching the seeker head, even if a relatively small and thus pivotable anechoic chamber is used. The radar transmitter is fixedly arranged in this hollow body. Relatively large angles of the line-of-sight of, for example, +60.degree. in azimuth and elevation can be simulated with such a construction.
Modifications of the invention are subject matter of the sub-claims.